In the processing and packaging of eggs, the eggs are collected from the chickens and moved to a processing area where the eggs are properly oriented and deposited into trays, also known as flats, formed in a convoluted manner from molded pulp or, more recently, from molded plastic, to create pockets for holding individual eggs. Each egg tray typically contains thirty eggs, arranged in five rows of six eggs in each row. When the egg trays are oriented such that the eggs are arranged in six rows with five eggs in each row, the egg trays will stack vertically with the individual eggs in the pockets in the first tray being aligned with convoluted pockets on the underside of the next vertically positioned tray which is oriented 90 degrees to the adjacent egg tray. As a result, the eggs are not vertically aligned from one egg tray to the next vertically positioned egg tray in the stack of egg trays.
The processing and packaging of eggs has become highly automated over recent years, with many functions which were accomplished manually now being performed either completely or partially automatically by machinery. With the influx of automated machinery comes a high speed of operation, particularly with respect to various processing steps including, washing, grading and packaging of the eggs into individual egg trays.
Stacking egg trays for shipment requires that the alternate egg trays be oriented at a ninety degree rotation relative to the egg trays immediately above and/or below within the stack. As a result, the packing of egg trays for shipment has traditionally been a manual operation even though much of the processing and placement of the eggs into the trays is accomplished by automated machinery. Some effort, however, has been made to provide automated machinery for stacking egg trays for shipment.
In U.S. Pat. No. 3,509,995, granted on May 5, 1970, to Marvin E. Colaw, a machine for stacking reusable egg trays is disclosed in which the eggs have been removed from the egg trays and the egg trays not soiled by broken egg remains are collected and stacked in a vertical manner. Soiled trays are identified by a sensor and allowed to pass along the conveyor for discharge off the end rather than be added to the stack. The teachings of this reference do not appear to include a mechanism for rotating the egg trays so that after having the eggs removed the egg trays will have the same orientation to stack properly.
In U.S. Pat. No. 3,763,625, granted to Rudy Slavin, et al, on Oct. 9, 1973, a machine is disclosed for the placement of eggs into the egg trays and then moving the filled egg trays into a stack for shipment. The Slavin machine incorporates a complex egg tray accumulating mechanism that affects a rotation of alternate egg trays by a platform in which the orientation is controlled by a cam mechanism that is alternated by a toggle device. The egg trays after being oriented properly are raised by the platform into an elevated stack held by four pivoted dog devices that are mounted on an elevated frame. After a proper number of egg trays have been accumulated in the elevated stack, the stack is lowered onto the conveyor and moved to a position to be removed for shipment.
A mechanism for handling egg trays is disclosed in U.S. Pat. No. 3,792,784, granted on Feb. 19, 1974, to Jacob H. Mosterd. The apparatus for handling the egg trays is primarily a gripping mechanism that is mounted on a four-bar linkage that is operable to move individual egg trays laterally from one conveyor to a second conveyor. By operation of this mounted gripping mechanism, a stack of egg trays can be disassembled one tray at a time by the gripping mechanism engaging an egg tray from the stack an placing the egg tray on the second conveyor, while a elevating support ratchets upwardly to position the next tray in the stack for engagement thereof by the gripping mechanism. This elevating support is also rotatable through 90 degrees to re-orient the uppermost tray on the stack as desired for transfer to the second conveyor.
In a similar manner, the Mosterd gripping mechanism can be used to create a stack of egg trays having alternating orientations. The gripping mechanism can engage a single egg tray on the second conveyor and move the gripped egg tray laterally to position the egg tray on the elevated support. The elevated support can then ratchet down a prescribed distance to accommodate the next egg tray, while also rotating through 90 degrees so that the subsequent egg tray placed onto the egg tray previously placed on the elevated support is oriented in a rotated position relative to the egg tray beneath it. With the next egg tray moved by the gripping mechanism from the second conveyor to the elevated support, the elevated support is ratcheted down another prescribed distance and rotated back 90 degrees to the original position. In this manner, a stack of egg trays with alternating orientations can be created.
U.S. Pat. No. 4,765,487, granted on Aug. 23, 1988, to George Bliss, discloses an apparatus for stacking articles, including egg cartons and egg trays. Egg cartons are containers holding a dozen eggs in a corrugated tray with a lid that folds over to capture the eggs internally. Such egg cartons are typically how eggs are sold to consumers commercially. The Bliss apparatus accumulates three egg cartons on a single layer and then alternates the orientation of succeeding layers of egg cartons until the stack of egg cartons is completed. The alternating orientation of the layers of egg cartons is accomplished through a rotating table on which the egg cartons are accumulated into a layer and then rotated 90 degrees relative to the previous layer before being elevated into a stack. This same mechanism can also form a stack of standard egg trays, as is disclosed in the Bliss reference. The stack of egg trays is held in an elevated position by four hinged layer holders that are positioned to engage the peripheral underside of the egg tray.
A different configuration of an apparatus for forming a stack of alternating egg trays is found in U.S. Pat. No. 4,997,339, granted to Matheus Antonis on Mar. 5, 1991, in which the egg trays are oriented by a rotating table on which the incoming egg trays are position. A cam mechanism operates the rotation of the rotating table between orientations that are 90 degrees of rotation apart. Once the egg tray has been properly oriented, an elevator provided with opposing fingers that engage the peripheral underside of the egg tray and elevate the egg tray while moving the egg tray longitudinally to place the egg tray into a stack formation. The opposing fingers pivot to pass over any accumulated egg trays in the stack before moving around the circular path to engage a subsequent egg tray.
Similarly, the apparatus disclosed in U.S. Pat. No. 6,155,153, granted to Stephen Davison on Dec. 5, 2000, is designed to create a stack of egg cartons in which alternating layers are oriented at a 90 degree rotation relative to the adjacent layers of egg cartons. As with the preceding devices described above, the orientation of the layer of egg cartons is affected by a rotating table. The Davison apparatus is also operate to form a stack of egg trays by rotating the alternating egg tray on the rotating table before being placed on top of the formed stack of egg trays.
The provision of rotating tables to affect the alternating orientation of the egg trays placed into a stack for shipment creates design problems as the table requires room to operate from beneath the egg tray to provide the structure for operatively rotating the table. Furthermore, high speeds of operation associated with mechanized handling of eggs require a more effective manner, other than a rotating table or manually turning the egg trays to create the stack of egg trays ready for shipment to a processor. Accordingly, it would be desirable to provide a machine for stacking filled egg trays in alternating orientations that does not utilize a rotating table in the orienting of the alternating egg trays. It is also desirable to provide an automatic egg tray stacking machine that will support the partially formed stack of egg trays with a lifter mechanism that engages all four sides of the lowermost egg tray in the partially formed stack.